Characteristics Of Buffeting Forces On Rectangular Cylinder And Streamlined Box Girder

Inspired by classic spectral tensor theory of turbulence, the three-dimensional buffeting forces model is applied to identify the two-wavenumber spectrum and aerodynamic admittance, which can be can be validated in wind tunnel experiments. In order to study the mechanism of fluid-structure interaction and the corresponding pattern of enery transition on rectangular cylinder and streamlined box girder used in bridge engineering, a series of wind tunnel experiments are carried out. Then, a mathematical coherence model of buffeting forces on bluff bodies is presented. For the purpose of engineering application, a practical three-dimensinal buffeting force model is proposed to predict the buffeting response of long span bridge. The main research contents of this thesis are shown as follows:1. The spectral tensor theory of isotoropic turbulence, the theroretical models for buffeting force and aerodynamic admittance on thin aerofoil and bridges are list. The problems in the current buffeting analysis are also discussed.2. Based on three-dimensional theory, a general approach, expressed in terms of a two-dimensional Fourier transform of the correlation of the buffeting force, is proposed to identify the two-wavenumber spectrum and aerodynamic admittance of the buffeting force. It is essential that the approach presented can be applided directly in wind tunnel experiments. A double-exponent coherence model of buffeting force, which is of strict physical significance, is derived based on a practical three-dimensional buffeting analysis approach. And then, the spanwise correlation of buffeting force is confirmed to be larger than that of turbulence theoretically for any situation. In addition, the present approach can be extended to study the three-dimensionality of the buffeting force on line-like structures with arbitrary cross-configurations.3. A series of simultaneous measurements of the surface pressures on section models with rectangular cross-section are carried out to study the spatial distribution of buffeting force, fluid-structure interaction mechanism and the pattern of energy transition. In addition, the effects of the dimension of rectangular cylinder and integral length scale of turbulence on the spanwise correlation of the buffeting force are also studied. Then, a mathematical coherence model for buffeting forces acting on rectangular cylinder is proposed.4. With respect to streamlined box girder, simultaneous measurements of the surface pressure on sectional models with different scale ratio are carried out to establish a general coherence model. For the purpose of engineering application, a pratical three-dimensional buffeting force model is presented based on the proposed coherence model. In the end, a long span cable-stayed bridge is taken as an example for illustrating the application of proposed three-dimensional approach in buffeting response analysis of long span bridge.